Transfer System for Transporting Work Pieces in a Press

ABSTRACT

A transfer system ( 100 ) for transporting work pieces in a press ( 1 ), comprises a transfer rail ( 150 ) having a plurality of grippers ( 152 ) for gripping the work pieces, a linear mechanism ( 110 ) attachable to a press frame ( 2 ) of the press ( 1 ) for linearly moving the transfer rail ( 150 ) with respect to the press frame ( 2 ) and an articulated mechanism ( 130 ) for carrying the transfer rail ( 150 ), the articulated mechanism ( 130 ) comprising at least three parallel swivel axes, whereby the articulated mechanism ( 130 ) is attached to the linear mechanism ( 110 ) such that it is linearly moveable with respect to the press frame ( 2 ). Articulated mechanisms are widely used and cost-effective. They allow for a simple construction of the transfer system. Furthermore, they allow for a very precise control. The linear mechanism and the main part of the articulated mechanism may be arranged on an outer side of the press frame, whereby only the transfer rail and the foremost part of the articulated mechanism to which the transfer rail is attached enter the press window. Therefore, the mechanism is well suited for presses with a small press window.

TECHNICAL FIELD

The invention relates to a transfer system for transporting work piecesin a press, comprising a transfer rail having a plurality of grippersfor gripping the work pieces and a linear mechanism attachable to apress frame of the press for linearly moving the transfer rail withrespect to the press frame. The invention further relates to a press, inparticular to a press line or multiple-die press, to a method fortransporting work pieces in a press and to the use of an articulatedrobot for transporting work pieces in a press.

BACKGROUND ART

An important step of the manufacture of components made of sheet metalis the forming step. Sheet metal parts are formed in a press, such as ahydraulic, hydroforming, mechanical, electrical or pneumatic press,typically including an upper die and a corresponding lower die. The diesare moved against each other, and thereby the work piece arranged in thework space between the dies is formed. The form of the dies determinesthe impact on the work piece and therefore the resulting form. Usually,a succession of forming steps using differently shaped dies is necessaryuntil the desired form of the sheet metal part is obtained. To performthese steps in an expedient way, a plurality of presses is arrangedsuccessively to form a press line, or a press is employed that includesa plurality of die pairs. On one hand, the capacity of the press line ormultiple-die press is determined by the capacity of the press, i. e. thetime required for carrying out one forming operation. On the other handhowever, the capacity significantly depends on the efficiency of thetransport of the work pieces from one press station to the next one. Itis therefore important to employ a fast transfer system forautomatically transporting work pieces from one press station to thenext one.

Most presses feature a press frame that supports the lower and upperdies of the press as well as corresponding drives and gears. The workpieces are transferred through a continuous window of the press frame,along a main transfer direction. For this purpose, a transfer systemcomprising a transfer rail having a plurality of grippers for grippingthe work pieces is provided. The work pieces may be gripped by magneticor suction tools or by grippers that engage with matching recesses orprotrusions of the work pieces or of holders attached to the workpieces. Often, such transfer systems are arranged within the window ofthe press, i. e. substantially on the inner side of the press frame.

However, in the case of small window dimensions there is not enoughspace for arranging the transfer system within the window and thereforethe main portion of the system has to be arranged on the outer side ofthe press frame. Only the transfer rail runs inside the press window andonly a small part of the support of the transfer rail enters the windowfrom the outside of the press. As an example, the “gullWing” transfersystem of Güdel pressAutomation, Langenthal, Switzerland is speciallyadapted for new or retrofit press applications with small windowdimensions. This system features a horizontal transfer rail runningparallel to the main transfer direction which is attached to the pressframe by serial kinematics, comprising in serial progression from thepress frame to the transfer rail a swivel axis parallel to the maintransfer direction, a vertical linear axis parallel to the main transferdirection, a first horizontal linear axis perpendicular to the maintransfer direction and a second horizontal linear axis parallel to themain transfer direction. With respect to the press frame, the transferrail is linearly moved along the main transfer direction by the secondhorizontal linear axis. The swivel axis exclusively serves for tippingup the whole system clear of the press, e.g. for allowing access to thebolster for changeover.

The “gullWing” system features an elaborate construction which is welladapted for heavy work pieces and fast dynamics. However, due to itscomplexity, the construction is rather costly.

SUMMARY OF THE INVENTION

It is the object of the invention to create a transfer system pertainingto the technical field initially mentioned, that is adapted to smalldimensions of the press window and that is of a simple construction.

The solution of the invention is specified by the features of claim 1.According to the invention, the transfer system features an articulatedmechanism for carrying the transfer rail, the articulated mechanismcomprising at least three parallel swivel axes, whereby the articulatedmechanism is attached to the linear mechanism such that it is linearlymoveable with respect to the press frame.

Articulated mechanisms are widely used and cost-effective. They allowfor a simple construction of the inventive transfer system. Furthermore,articulated mechanisms allow for a very precise control, therepeatability of such mechanisms may be of the order of 0.1 mm. In thecase of presses with small window dimensions, the linear mechanism andthe main part of the articulated mechanism may be arranged on an outerside of the press frame, whereby only the transfer rail and the foremostpart of the articulated mechanism to which the transfer rail is attachedenter the press window. The three parallel swivel axes of thearticulated mechanism allow for arbitrarily moving the attachment pointof the transfer rail in a plane that is perpendicular to the three axes.At the same time, the orientation of the transfer rail and its grippersin said plane may be as well arbitrarily chosen. The degree of freedomof the linear mechanism must not run in said plane such that by means ofthe linear mechanism movements of the attachment point leading outsideof said plane are enabled.

The inventive transfer system may be used in an inventive method fortransporting work pieces in a press, comprising the steps of

-   -   a) positioning the transfer rail in a first position, such that        a work piece to be transported is seizable by a plurality of the        grippers attached to the transfer rail;    -   b) seizing the work piece by actuating the grippers;    -   c) lifting the transfer rail together with the work piece by        moving along a linear axis of the linear mechanism and/or by        moving around at least one swivel axis of the at least three        swivel axes of the articulated mechanism;    -   d) transferring the work piece by moving the transfer rail along        a main transfer direction by moving the articulated mechanism        and/or the linear mechanism;    -   e) lowering the transfer rail together with the work piece by        moving the linear mechanism and/or the articulated mechanism;        and    -   f) releasing the work piece by actuating the grippers of the        transfer rail.

In first preferred embodiments of the invention, the linear mechanismcomprises a horizontal linear guide attachable to the press frame, insuch a way that its linear degree of freedom runs parallel to the maintransfer direction of the press. Thereby, the linear mechanism allowsfor linearly moving the articulated mechanism together with the transferrail in a direction parallel to the main transfer direction. Theremaining degrees of freedom needed for the transfer rail are providedby the articulated mechanism. The linear guide may e. g. be a rail onwhich a carriage is linearly movable, a slide bearing or a spindleguide.

In the case of a horizontal linear degree of freedom running parallel tothe main transfer direction, the at least three swivel axes arepreferably oriented parallel to the horizontal linear guide. Therefore,the swivel axes allow for arbitrarily moving the foremost end of thearticulate mechanism in a vertical plane perpendicular to the maintransfer direction. Together with the linear mechanism, the transferrail is arbitrarily movable (within certain limits imposed by the actualconstruction of the mechanisms). At the same time, the orientation ofthe transfer rail and its grippers within said vertical plane may bearbitrarily chosen, in particular a change of orientation of thetransfer rail caused by swiveling motions around the two swivel axesfurther away from the transfer rail may be compensated by the third,foremost swivel axis. For example, this allows for retaining ahorizontal orientation of the transfer rail and its grippers, whilemoving the transfer rail vertically or horizontally, in a directionperpendicular to the main transfer direction.

Alternatively, the swivel axes are oriented inclined to the horizontallinear guide. In this case, it is still possible to move the transferrail as needed in a transfer process in a press by combining linearmotions along the horizontal linear guide and swiveling motions aroundthe three axis. However, in the case of inclined swivel axes the linearmotion along the main transfer direction is not decoupled from themovements in the plane perpendicular to the swivel axes, and thereforeswiveling actions to move the transfer rail vertically or horizontally,across the press, have to be compensated by corresponding linearmovements along the horizontal guide.

Advantageously, the horizontal linear guide is attachable to the pressframe in a position above the work space of the press, and thearticulated mechanism is attached to the linear guide in a suspendedposition. This arrangement avoids obstructions of the lateral openingsof the press frame, thereby allowing for easy access to the dies andtools within the press.

Alternatively, the horizontal linear guide is attachable to a baseportion of the press frame, and the articulated mechanism is supportedon the linear guide.

In second preferred embodiments of the invention, the linear mechanismcomprises a vertical linear guide attachable to the press frame, suchthat the articulated mechanism attached to the linear mechanism islinearly movable in a vertical direction. Furthermore, the at leastthree swivel axes are oriented parallel to the vertical linear guide.Arranged like this, the swivel axes allow for arbitrarily moving theforemost end of the articulate mechanism, to which the transfer rail isattached, in a horizontal plane. Together with the linear mechanism, thetransfer rail is arbitrarily movable (within certain limits imposed bythe actual construction of the mechanisms). At the same time, theorientation of the transfer rail and its grippers within said horizontalplane may be arbitrarily chosen, in particular a change of orientationof the transfer rail caused by swiveling motions around the two swivelaxes further away from the transfer rail may be compensated by thethird, foremost swivel axis. For example, this allows for retaining ahorizontal orientation of the transfer rail and its grippers, whilemoving the transfer rail horizontally.

Again, the linear guide may e. g. be a rail on which a carriage islinearly movable, a slide bearing or a spindle guide.

Preferably, two linear mechanisms with vertical linear guides areattachable to two supports of the press frame. A first articulatedmechanism is attached to the first of said linear mechanisms, and asecond articulated mechanism is attached to the second of said linearmechanisms. The transfer rail is attached to both the first articulatedmechanism and the second articulated mechanism. Attaching the transferrail to two separate articulated mechanisms, preferably near oppositeends of the transfer rail, ensures stable support of the transfer railand facilitates the handling of heavy work pieces. Furthermore, the twolinear guides may be attached to two vertical supports at opposite endsof the press or press station.

Preferably, the movements of the first articulated mechanism and thesecond articulated mechanism are synchronized by an external controlsystem, such as an electronic control system for the entire press or acentral control system for the transfer system. The control systemensures that the articulated mechanisms (and preferably as well thelinear mechanisms) are synchronously actuated. Note, that in the case oftwo vertically movable articulated mechanisms holding a single transferrail it is not required to actively control the rotational position ofthe third swivel axis, adjacent to the transfer rail. This is becausethe orientation of the transfer rail with respect to a vertical axis ispredetermined by the positions of the two attaching elements of thearticulated mechanisms.

Alternatively, especially in cases where heavy work pieces are not to beprocessed, the transfer rail is attached to a single articulatedmechanism, preferably in a central region of the transfer rail.

Advantageously, the at least three swivel axes are constructed andarranged such that the articulated mechanism may be swiveled out clearof the press. Thereby, the articulated mechanism is removed from thevicinity of the lateral openings of the press frame and therefore thedies and tools within the press may be more easily accessed.Furthermore, in the case of a horizontal linear mechanism the transferrail may be swiveled out clear of the press together with thearticulated mechanism if the length of the transfer rail does not exceedthe corresponding dimensions of the lateral opening. Additionally, thethree swivel axes allow for positioning the transfer rail in a positionoutside of the press which is convenient for maintenance or toolexchange, especially in the case where the three swivel axes areparallel to the main transfer direction.

Preferentially, the articulated mechanism comprises an automatic couplerfor coupling the transfer rail. This allows for easy and efficient toolchange, in particular in cooperation with feeders or robots forproviding the transfer rail to be changed. The couplers may be actuatedelectrically, hydraulically or pneumatically. They are preferablycontrolled by an external control system, such as an electronic controlsystem for the entire press or a central control system for the transfersystem.

Alternatively, the transfer rails are manually attached to and releasedfrom the articulated mechanism.

Preferably, the articulated mechanism is constituted by a robot arm ofan articulated robot having at least three parallel swivel axes.Articulated robots are widely available, therefore the inventivetransfer system may be assembled from a few stock items, which reducesthe system's cost. Often, usual articulated robots feature more thanthree swivel axes because they are intended for rather complex handlingoperations. For example, the articulated robots of the roboFlex seriesof Güdel AG, Langenthal, Switzerland, feature six axes of motion, out ofthem one linear axis, three parallel swivel axes and two furtherrotational axes. While such robots are useable in the context of theinvention, for transporting work pieces in a press, in principlearticulated robots of a simpler construction, having only three parallelswivel axes, suffice. The linear mechanism may be an integrated axis ofmotion of the robot or it may be provided separately. Similarly, thedrive for the linear mechanism may be arranged at the linear guide, at acarriage running along the linear guide, carrying the articulatedmechanism, or at the articulated mechanism itself. Finally, using anarticulated robot allows for employing existing robot control systems.

Alternatively, the articulated mechanism may be a dedicated mechanismwhich is not based on existing articulated robots.

Advantageously, the articulated mechanism comprises

-   -   a) a base attached to the linear mechanism;    -   b) a first arm attached to said base via a first of said swivel        axes;    -   c) a second arm, a first end of which is attached to said first        arm, via a second of said swivel axes, and a second end of which        is attached to the transfer rail, via a third of said swivel        axes;    -   d) a first drive for actuating a swiveling motion of said first        arm with respect to said base, around said first swivel axis;    -   e) a second drive for actuating a swiveling motion of said        second arm with respect to said first arm, around said second        swivel axis;    -   f) a third drive for actuating a swiveling motion of the        transfer rail with respect to said second arm, around said third        swivel axis.

Preferably, the first drive is attached to the base, the second drive isattached to the first arm and the third drive is attached to the secondarm. This allows for simultaneously minimizing the masses to be movedwhile preserving constructional simplicity by avoiding complextransmissions. The drives may be supplied with energy (electricity,hydraulic or pneumatic pressure) e. g. by cable drag chains.

Alternatively, only two drives are provided for actuating movementsaround swivel axes and the movement around the third swivel axis ismechanically synchronized to the movements around the two other swivelaxes in such a way that the orientation of the transfer rail ispreserved, e. g. by sort of a parallelogram linkage for the attachmentpoint of the transfer rail. The mechanical synchronization isautomatically provided in cases where the transfer rail is supported bytwo articulated mechanisms.

In a press, in particular a press line or multiple-die press, theinventive transfer system may be employed in various ways. Firstly, asingle transfer system may be arranged at one side of the press,carrying a usual transfer rail which grips the work pieces on one oftheir lateral sides or which features a cross-bar that extends acrossthe press. In the case of heavier work pieces, two transfer systems maybe arranged across the press, each of them carrying a separate transferrail for simultaneously gripping the work pieces on two opposite sides.Finally, the two transfer systems arranged across the press may both beattached to a cross-bar which extends across the press and which gripsthe work pieces from above, e. g. by means of suction or magnetic tools.This arrangement is particularly advantageous in the case of heavy workpieces or if it is required that the work pieces are gripped in acentral region, close to the longitudinal axis of the press.

Other advantageous embodiments and combinations of features come outfrom the detailed description below and the totality of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings used to explain the embodiments show:

FIG. 1 A front view of a first embodiment of a n inventive transfersystem, featuring a horizontal linear guide;

FIG. 2 a side view of the transfer system of FIG. 1;

FIG. 3A-D side views of different positions of the articulated mechanismof the transfer system of FIG. 1 during the transfer process;

FIG. 4 a front view of a second embodiment of an inventive transfersystem, featuring vertical linear guides;

FIG. 5 a top view of the transfer system of FIG. 4;

FIG. 6A-D top views of different positions of one of the articulatedmechanisms of the transfer system of FIGS. 4, 5 during the transferprocess;

FIG. 7 a top view of a rest position of one of the articulatedmechanisms of the transfer system of FIGS. 4, 5.

In the figures, the same components are given the same referencesymbols.

Preferred Embodiments

FIG. 1 is a schematic illustration of a front view of a first embodimentof an inventive transfer system, featuring a horizontal linear guide. Amultiple-die press 1 features a press frame 2 comprising vertical posts3, 4 supporting the upper dies 5 and the corresponding drives and gearsarranged in a housing 6. Note, that the construction of the press 1,which has a substantially rectangular footprint, is symmetrical, i. e.across the press another pair of vertical posts are arranged forsupporting the upper dies 5 and the housing 6. The four vertical postsdefine a substantially rectangular work space. The lower dies 7 aresupported on a floor-based press bed 8. The dies 5, 7 and thecorresponding mechanisms for moving the upper dies 5 are as such knownin the field of press technology and are not shown in detail. Along amain transfer direction 9 a sequence of corresponding upper and lowerdies 5, 7 are provided, on opposite sides of a press window 10 in whichwork pieces are formed in a plurality of forming steps.

The work pieces are transported from a die pair to the next adjacent diepair by a transfer system 100. The transfer system 100 comprises alinear mechanism 110, an articulated mechanism 130 and a transfer rail150 attached to the articulated mechanism 130. The linear mechanism 110features a horizontal bar 111 that is arranged at the outer side of thepress frame 2 in a vertical position above the work space for formingthe work pieces between the upper dies 5 and the lower dies 7. Thehorizontal bar 111 is attached to the two lateral vertical posts 3, 4 bycorner profiles 112, 113. It has a substantially square profile andfeatures a horizontal guide rail 114 constructed along its lowersurface. A carriage 115 featuring a drive 116 is horizontally runningalong the guide rail 114 (linear axis J₁).

The articulated mechanism 130 is attached to the carriage 115 andfeatures three parallel swivel axes J₂, J₃, J₄ is described in moredetail in connection with FIG. 2, which is a schematic illustration of aside view of the transfer system of FIG. 1, in a plane that isperpendicular to the main transfer direction 9 of FIG. 1. FIG. 2 againillustrates the press 1 with the press frame 2, the upper dies 5, thehousing 6 for the drives and gears for the upper dies 5 and the pressbed 8 supporting the lower dies 7. Visible in FIG. 2 is one of thevertical posts 3 to which the horizontal bar 111 of the linear mechanism110 is attached by means of the corner profile 112. The transversalwidth of the linear guide rail 114 attached to the lower surface of thehorizontal bar 111 is slightly larger than the width of the horizontalbar 111 such that the rail protrudes from the horizontal bar 111 on itsouter as well as on its inner transversal side.

The carriage 115 is running on the linear guide rail 114 by means ofrolls 117 supported on the protruding portions of the guide rail 114.Drive pinions 118 are pressed against a rack arranged on the lowersurface of the guide rail 114, opposite to the rolls 117. The drivepinions 118 are driven by drive 116 in order to move the carriage 115along the horizontal bar 111. The drive 116 comprises an electric motorwhich is fed by a cable drag chain which is as such known from prior artand which is not displayed in the Figures for the benefit of lucidity.The cable drag chain may e. g. run in a suitable profile arranged on topof the horizontal bar 111. Thereby, the transfer system 100 and thelateral openings to the press window 10 are not obstructed.

The carriage 115 features an upper portion 119 featuring the rolls 117and drive pinions 118 as well as a lower portion 120 to which the drive116 is attached and which features—as part of the articulated mechanism130—an axle 131 which is oriented horizontally, parallel to thehorizontal bar 111 and therefore parallel to the main transferdirection. The axle 131 is coupled to a drive 132 (see FIG. 1), attachedto the lower portion 120 of the carriage 115, for actuating movementsaround the axle 131, corresponding to the first swivel axis J₂. A firstarm 133 of the articulated mechanism 130 is rotatably supported on theaxle 131. A drive 134 comprising another electrical motor is attached toan upper portion of the first arm 133, coaxial with the first swivelaxis J₂. Its movements are transmitted to an axle 135 situated near thelower end of the first arm 133, e. g. by means of a belt or shaft drive,in order to actuate movements around the axle 135 corresponding to thesecond swivel axis J₃. A second arm 136 of the articulated mechanism 130is rotatably supported on said axle 135. Again, a drive 137 (see FIG. 1)with an electrical motor is attached to the portion of the second arm136 supported on the axle 135 of the first arm 133. The movements of thedrive 137 are transmitted to another axle 138 situated near the otherend of the second arm 136 (again e. g. by a belt or shaft drive).Thereby movements around the axle 138 are actuated, corresponding to thethird swivel axis J₄. An attaching element 139 for the transfer rail 150is rotatably supported on the axle 138 of the second arm 136.

The transfer rail 150 features a longitudinal rod 151 and a plurality ofgrippers 152 that feature suitable grip means (not displayed) for thework pieces to be transported, such as magnetic or suction tools orother elements that are suitable for gripping the work pieces. Thetransfer rail 150 and/or the grippers 152 may feature additional(rotational or translational) degrees of freedom such that gripping ofthe work pieces is facilitated or such that the orientation of the workpieces may be changed during the transfer process.

FIGS. 3A-D are schematic side views of different positions of thearticulated mechanism of the transfer system of FIG. 1 during thetransfer process. The FIG. 3A displays a starting position where thetransfer rail 150 is situated in a lowered position outside the actualwork space between the upper and lower dies 5, 7. The work piece 11 tobe transported (which may be a single work piece, a plurality of workpieces or one or several pallets for holding the actual work pieces) islocated on the lower die 7. Starting from the displayed position, thetransfer rail 150 is moved horizontally towards the center of the press1. For this purpose, the first arm 133 of the articulated mechanism 130is rotated counter-clockwise around the first swivel axis J₂. Tocompensate the vertical movement of the transfer rail 150 effected bythe rotation of the first arm 133 the second arm 136 of the articulatedmechanism 130 is rotated clockwise around the second swivel axis J₃.

The FIG. 3B displays the situation in which the gripper 152 of thetransfer rail 150 has engaged with the work piece 11 (or with a contactpiece attached to the work piece 11, respectively). The transfer rail150 is still in a lowered position and has reached its innermostposition needed during the displayed transfer process. However, inprinciple the transfer system 100 is capable of positioning the transferrail 150 in positions that are far more inside the press, which isnecessary if the work pieces to be transported have a width that is muchsmaller than the width of the press 1.

Next, the second arm 136 of the articulated mechanism 130 is rotatedcounter-clockwise around the second swivel axis J₃ in order to lift thetransfer rail 150. At the same time, the first arm 133 is rotatedcounter-clockwise around the first swivel axis J₂ to compensate lateralmovements. Furthermore, the attaching element 139 is rotated clockwisearound the third swivel axis J₄ such that a change of orientation of thetransfer rail 150 due to the rotation of the second arm 136 iscompensated, i. e. the orientation of the transfer rail is preserved.

FIG. 3C displays the situation after the transfer rail 150 has beenlifted into its upper position. It is this position in which the workpiece 11 is transferred along the main transfer direction by actuatingthe linear mechanism 110. After the linear transport, the transfer rail150 is again lowered in order to deposit the work piece 11 on the nextadjacent lower die 7. For this purpose, the second arm 136 is rotatedclockwise around the second swivel axis J₃ and the first arm 133 isrotated clockwise around the first swivel axis J₂. The orientation ofthe transfer rail 150 is preserved by simultaneously rotating theattaching element 139 counter-clockwise around the third swivel axis J₄.Please note, that depending on the form and size of the work piece 11and of the dies 5, 7 the lowering of the transfer rail 150 may startbefore the linear transport along the horizontal bar 111 has finished,in order to speed up the transfer process.

After the work piece 11 has been deposited on the lower die 7, as shownin FIG. 3D, the transfer rail 150 is again horizontally retracted fromthe press 1. This is achieved by rotating the first arm 133 of thearticulated mechanism 130 clockwise around the first swivel axis J₂.Again, to compensate the vertical movement of the transfer rail 150effected by the rotation of the first arm 133 the second arm 136 of thearticulated mechanism 130 is rotated around the second swivel axis J₃,this time counter-clockwise.

After linearly returning the articulated mechanism 130 to its startposition by means of the linear mechanism 110 the situation displayed inFIG. 3A is reached again, such that the next transfer step may beeffected as soon as the forming step is finished. Note that a pluralityof work pieces are generally simultaneously transported by the transferprocess, engaged by different grippers 152 of the transfer rail 150 (orarranged on a common holder or pallet).

FIG. 4 is a schematic illustration of a front view of a secondembodiment of an inventive transfer system, featuring vertical linearguides.

The multiple-die press 1 corresponds to the press described inconnection with the first embodiment of the invention (FIGS. 1-3).Again, it features the press frame 2 comprising vertical posts 3, 4 (andanother two posts across the press) supporting the upper dies 5 and thecorresponding drives and gears arranged in the housing 6. The lower dies7 are supported on the floor-based press bed 8. Along the main transferdirection 9 a sequence of corresponding upper and lower dies 5, 7 areprovided, on opposite sides of a pres s window 10 in which the workpieces are formed in a plurality of forming steps.

The work pieces are transported from a die pair to the next adjacent diepair by a transfer system 200 that comprises two linear mechanisms210.1, 210.2, two corresponding articulated mechanisms 230.1, 230.2 anda transfer rail 250 attached to both the articulated mechanisms 230.1,230.2. In contrast to the first embodiment, the linear and articulatedmechanisms 210.1, 230.1; 210.2, 230.2 are constituted by two stockarticulated robots (such as the roboFlex series of Güdel AG, Langenthal,Switzerland) having six axes (one linear axis and five rotational axes)J₁-J₆. Note that both the first embodiment described above may as wellbe equipped by stock articulated robots (featuring at least the fourneeded axes) and the second embodiment may be equipped by dedicatedlinear/articulated mechanisms as described in connection with the firstembodiment.

The linear mechanisms 210.1, 210.2 feature vertical bars 211.1, 211.2that are arranged at the outer side of the press frame 2 by means ofbooms 221.1, 221.2. These booms 221.1, 221.2 are attached to thevertical posts 3, 4 by corner profiles 212, 213 and hold the verticalbars 211.1, 211.2 in a suspending manner, in positions that arediagonally outside the vertical posts 3, 4 with respect to the maintransfer direction 9 as well as with respect to the transverse direction(see also FIG. 5). The vertical bars 211.1, 211.2 have a substantiallysquare profile and feature vertical guide rails 214.1, 214.2 constructedalong their transversally inner surface (see FIG. 5). Carriages 215.1,215.2 featuring drives 216.1, 216.2 run vertically along the guide rail214.1, 214.2 (linear axis J₁). The articulated mechanisms 230.1, 230.2are attached to the carriages 215.1, 215.2 and feature three parallelswivel axes J₂, J₃, J₄. The height of the linear mechanisms 210.1, 210.2is chosen such that the transfer rail 250 attached to the articulatedmechanisms 230.1, 230.2 is vertically displaceable in the press window10. The articulated mechanisms 230.1, 230.2 are constructed and arrangedreversed left to right with respect to each other and described in moredetail below, in connection with FIG. 5.

FIG. 5 is a schematic illustration of a top view of the transfer systemof FIG. 4, in a horizontal plane that is in a height above the booms221.1, 221.2 of the transfer system 200. The upper dies and thecorresponding housing are not displayed for clarity of the illustration.Visible are the press bed 8 supporting the lower dies 7, as well as thevertical posts 3, 4 supporting the linear mechanisms 210.1, 210.2 bymeans of booms 221.1, 221.2 attached to the vertical posts 3, 4 bycorner profiles 212, 213. In the following, we discuss one of the twolinear/articulated mechanisms 210.1, 230.1; 210.2, 230.2. As remarkedabove, the other just corresponds to a mirror image of this one.

The width of the linear guide rail 214.1 attached to the inner surfaceof the vertical bar 211.1 is slightly larger than the width of thevertical bar 211.1, such that the guide rail 214.1 protrudes from thevertical bar 211.1 on its left as well as right side. The carriage 215.1is running on the linear guide rail 214.1 by means of rolls 217.1co-operating with drive pinions 218.1 pressed against a rack arranged onthe inner surface of the guide rail 214.1, opposite to the rolls 217.1.The drive pinions 218.1 are driven by drive 216.1 in order to move thecarriage 215.1 up and down along the vertical bar 211.1. The drive 216.1comprises an electric motor which is fed by a cable drag chain which isas such known from prior art and which is not displayed in the Figuresfor the benefit of lucidity. The cable drag chain may e. g. run in asuitable vertically oriented profile arranged outside or behind thevertical bar 211.1. Thereby, the transfer system 200 and the lateralopenings to the press window 10 are not obstructed.

The carriage 215.1 features an outer portion 219.1 featuring the rolls217.1 and drive pinions 218.1 as well as an inner portion 220.1 to whichthe drive 216.1 is attached and which features—as part of thearticulated mechanism 230.1—a vertically oriented axle 231.1. The axle231.1 is coupled to a drive (arranged on the bottom side of the innerportion 220.1 and therefore not visible in FIG. 5) for actuatingmovements around the axle 231.1, corresponding to the first swivel axisJ₂. A first arm 233.1 of the articulated mechanism 230.1 is rotatablysupported on the axle 231.1. A drive 234.1 comprising another electricalmotor is attached to the upper side of an outer portion of the first arm233.1, coaxial with the first swivel axis J₂. Its movements aretransmitted to an axle 235.1 situated near the inner end of the firstarm 233.1, e. g. by means of a belt or shaft drive, in order to actuatemovements around the axle 235.1 corresponding to the second swivel axisJ₃. A second arm 236.1 of the articulated mechanism 230.1 is rotatablysupported on said axle 235.1. Three drives 237.1, 240.1, 241.1 withelectrical motors are attached to the outer end of the second arm 236.1.The movements of one of the drives 237.1 are transmitted to another axle238.1 situated near the other end of the second arm 236.1 (again e. g.by a belt or shaft drive). Thereby, movement around the axle 238.1 isactuated, corresponding to the third swivel axis J₄. An attachingelement 239.1 for the transfer rail 250.1 is rotatably supported on theaxle 238.1 of the second arm 236.1. The other two drives 240.1, 241.1attached to the second arm 236.1 are used for actuating two other swivelaxes of the articulate robot, that are not used in the context of thetransfer system 200, namely an axis (J₅) which is coaxial with thesecond arm 236.1, allowing for rotating an inner section of the secondarm 236.1 with respect to the outer section of said second arm 236.1,and an axis (J₆) that is coaxial with the attaching element 239.1,allowing for rotating an end piece of the attaching element 239.1 withrespect to the base piece of the attaching element 239.1.

The transfer rail 250 attached to both the articulated mechanisms 230.1230.2 again features a longitudinal rod 251 and a plurality of grippers252 that feature suitable grip means (not displayed) for the work piecesto be transported such as magnetic or suction tools or other elementsthat are suitable for gripping the work pieces.

FIGS. 6A-D show schematic top views of different positions of one of thearticulated mechanisms of the transfer system of FIGS. 4, 5 during thetransfer process. The FIG. 6A displays a starting position where thetransfer rail 250 is situated in a lowered position outside the actualwork space. The work piece 11 to be transported (which may be a singlework piece, a plurality of work pieces or one or several pallets forholding the actual work pieces) is located on the lower die 7. Startingfrom the displayed position, the transfer rail 250 is moved horizontallytowards the center of the press 1. For this purpose, the first arm 233.1of the articulated mechanism 230.1 is rotated clockwise around the firstswivel axis J₂, and at the same time the second arm 236.1 of thearticulated mechanism 230.1 is rotated counter-clockwise around thesecond swivel axis J₃. The orientation of the transfer rail 250 ispreserved by slightly rotating the attaching element 239.1 clockwisearound the swivel axis J₄.

FIG. 6B displays the situation in which the grippers 252 of the transferrail 250 have engaged with the work piece 11 (or with a contact pieceattached to the work piece respectively). The transfer rail 250 is stillin a lowered position and has reached its innermost position neededduring the displayed transfer process. However, in principle thetransfer system 200 is capable of positioning the transfer rail 250 inpositions that are far more inside the press, which is necessary if thework pieces to be transported have a width that is much smaller than thewidth of the press 1.

Next, the transfer rail 250 is lifted into its upper position byactuating the linear mechanism 210.1. Following this, the second arm236.1 of the articulated mechanism 230.1 is rotated clockwise around thesecond swivel axis J₃ in order to move the transfer rail 250 along themain transfer direction 9. In order to preserve the transversal positionof the transfer rail 250, the first arm 233.1 is at the same timerotated clockwise around the first swivel axis J₂. The attaching element239.1 is rotated counter-clockwise around the third swivel axis J₄ inorder to compensate its change of orientation due to the simultaneousclockwise rotations of both the arms 233.1, 236.1. Note, that it is notnecessary to actively control the rotation around the third swivel axisJ₄ because the respective orientation of the transfer rail 250 isalready defined by the positions of the two attaching elements 239.1 ofthe two articulated mechanisms 230.1.

FIG. 6C displays the situation after the transfer rail 250 has reachedits end position with respect to the main transfer direction 9. Now, thetransfer rail 250 is lowered by the linear mechanism 210.1 in order todeposit the work piece 11 on the next adjacent lower die 7. Please note,that depending on the form and size of the work piece 11 and of the diesthe lowering of the transfer rail 250 may start before the transportalong the main transfer direction 9 has finished, in order to speed upthe transfer process.

After the work piece 11 has been deposited on the lower die 7, thetransfer rail 250 is again horizontally retracted from the press 1. Thisis achieved by rotating the first arm 233.1 of the articulated mechanism230.1 counter-clockwise around the first swivel axis J₂ and by rotatingthe second arm 236.1 clockwise around the second swivel axis J₃. At thesame time, the attaching element 239.1 is rotated counter-clockwisearound the third swivel axis J₄.

After the situation displayed in FIG. 6D has been reached, the transferrail 250 is returned to its start position by simultaneously rotatingthe first arm 233.1 counter-clockwise around the first swivel axis J₂and rotating the second arm 236.1 clockwise around the second swivelaxis J₃. The orientation of the attaching element 239.1 is preserved byclockwise rotation around the third swivel axis J₄.

FIG. 7 is a schematical top view of a rest position of one of thearticulated mechanisms of the transfer system of FIG. 4. To return thearticulated mechanism 230.1 in its rest position the transfer rail isfirst separated from the attaching element 239.1. Preferably, this isdone automatically employing automatic couplers for the transfer rail.After the separation, the first arm 233.1 as well as the second arm236.1 are both rotated counter-clockwise around the first swivel axis J₂and the second swivel axis J₃ respectively. Thereby, the articulatedmechanism 230.1 is removed from the press window 10 and its spatialextensions in the main transfer and opposite directions. This allows forunhampered access to the dies of the press 1.

As a matter of course, the technical details of the discussedembodiments may be modified without leaving the scope of the invention,e. g. the construction and arrangement of the linear and articulatedmechanisms as well as of the transfer rail may be modified. Furthermore,the inventive conveyor system is appropriate for press lines as well asfor multiple-die presses of different press widths, lengths anddistances. A press or a press line may be equipped with a plurality ofserially arranged transfer systems.

The transfer system may be integrated into a variety of pressconfigurations, e. g. independent of the arrangement of the support forthe upper dies or of the press bed. The inventive conveyor system issuited for retrofitting of existing press lines or multiple-die pressesas well as for integration into newly built appliances. The transfersystem is not only suitable for transporting work pieces from a pressstation to the next adjacent press station but can as well be employedfor transporting work pieces from an initial feed station to a firstpress, to or from an intermediate deposit station or from a final pressto a delivery stack or further conveyor.

In summary, it is to be noted that the invention creates a transfersystem that is adapted to small dimensions of the press window and thatis of a simple construction.

1. A transfer system for transporting work pieces in a press, comprisinga) a transfer rail (150; 250) having a plurality of grippers (152; 252)for gripping the work pieces (11); b) a linear mechanism (110; 210.1,210.2) attachable to a press frame (2) of the press (1) for linearlymoving the transfer rail (150; 250) with respect to the press frame (2);characterized by c) an articulated mechanism (130; 230.1 230.2) forcarrying the transfer rail (150; 250), the articulated mechanism (130;230.1 230.2) comprising at least three parallel swivel axes (J₂, J₃,J₄), whereby the articulated mechanism (130; 230.1 230.2) is attached tothe linear mechanism (110; 210.1, 210.2) such that it is linearlymoveable with respect to the press frame (2).
 2. The transfer system asrecited in claim 1, characterized in that the linear mechanism (110)comprises a horizontal linear guide (111, 114) attachable to the pressframe (2), the guide (111, 114) being arranged parallel to a maintransfer direction (9) of the press (1) such that the articulatedmechanism (130) is linearly moveable parallel to the main transferdirection (9).
 3. The transfer system as recited in claim 2,characterized in that the at least three swivel axes (J₂, J₃, J₄) areoriented parallel to the horizontal linear guide (111, 114).
 4. Thetransfer system as recited in claim 2, characterized in that thehorizontal linear guide (111, 114) is attachable to the press frame (2)in a position above a work space of the press (1), and in that thearticulated mechanism (130) is attached to the linear guide (111, 114)in a suspended position.
 5. The transfer system as recited in claim 1,characterized in that the linear mechanism (210.1, 210.2) comprises avertical linear guide (211.1, 214.1; 211.2, 214.2) attachable to thepress frame (2), such that the articulated mechanism (230.1; 230.2) islinearly moveable in a vertical direction, and in that the at leastthree swivel axes (J₂, J₃, J₄) are oriented parallel to the verticallinear guide (211.1, 214.1; 211.2, 214.2).
 6. The transfer system asrecited in claim 5, characterized by a) a first linear mechanism (210.1)attachable to a first support (3) of the press frame (2); b) a secondlinear mechanism (210.2) attachable to a second support (4) of the pressframe (2); c) a first articulated mechanism (230.1) attached to thefirst linear mechanism (210.1); and d) a second articulated mechanism(230.2) attached to the second linear mechanism (210.2); whereby e) thetransfer rail (250) is attached to both the first articulated mechanism(230.1) and the second articulated mechanism (230.2).
 7. The transfersystem as recited in claim 6, characterized in that movements of thefirst articulated mechanism (230.1) and the second articulated mechanism(230.2) are synchronized by an external control system.
 8. The transfersystem as recited in claim 1, characterized in that the at least threeswivel axes (J₂, J₃, J₄) are constructed and arranged such that thearticulated mechanism (130; 230.1, 230.2) may be swiveled out clear ofthe press (1).
 9. The transfer system as recited in claim 1,characterized in that the articulated mechanism (130; 230.1, 230.2)comprises an automatic coupler for coupling the transfer rail (150;250).
 10. The transfer system as recited in claim 1, characterized inthat the articulated mechanism (230.1, 230.2) is constituted by a robotarm of an articulated robot having at least three parallel swivel axes(J₂, J₃, J₄).
 11. The transfer system as recited in claim 1 ,characterized in that the articulated mechanism (130; 230.1, 230.2)comprises a) a base (115; 215.1, 215.2) attached to the linear mechanism(110; 210.1, 210.2); b) a first arm (133; 233.1) attached to said base(115; 215.1) via a first of said swivel axes (J₂); c) a second arm (136;236.1), a first end of which is attached to said first arm (133; 233.1),via a second of said swivel axes (J₃), and a second end of which isattached to the transfer rail (150; 250), via a third of said swivelaxes (J₄); d) a first drive (132) for actuating a swiveling motion ofsaid first arm (133; 233.1) with respect to said base (115; 215.1),around said first swivel axis (J₂); e) a second drive (134; 234.1) foractuating a swiveling motion of said second arm (136; 236.1) withrespect to said first arm (133; 233.1), around said second swivel axis(J₃); f) a third drive (137; 237.1) for actuating a swiveling motion ofthe transfer rail (150; 250) with respect to said second arm (136;236.1), around said third swivel axis (J₄).
 12. The transfer system asrecited in claim 11, characterized in that the first drive (132) isattached to the base (115; 215.1, 215.2), in that the second drive (134;234.1) is attached to the first arm (133; 233.1) and in that the thirddrive (137; 237.1) is attached to the second arm (136; 236.1).
 13. Apress, in particular a press line or multiple-die press (1), comprisingat least one transfer system (100; 200) as recited in claim
 1. 14. Thepress as recited in claim 13, characterized in that a first transfersystem and a second transfer system are arranged across the press and inthat the transfer rail is a cross bar that is attached to both the firstand the second transfer system.
 15. A method for transporting workpieces in a press, using a transfer system, in particular one as recitedin claim 1, comprising a linear mechanism (110; 210.1, 210.2) attachableto a press frame (2) of the press (1) and an articulated mechanism (130;230.1 230.2) for carrying a transfer rail (150; 250), the articulatedmechanism (130; 230.1 230.2) comprising at least three parallel swivelaxes (J₂, J₃, J₄), whereby the articulated mechanism (130; 230.1 230.2)is attached to the linear mechanism (110; 210.1, 210.2) such that it islinearly moveable with respect to the press frame (2), the methodcomprising the steps of a) positioning the transfer rail (150; 250) in afirst position, such that a work piece (11) to be transported isseizable by a plurality of grippers (152; 252) attached to the transferrail (150; 250); b) seizing the work piece (11) by actuating thegrippers (152; 252); c) lifting the transfer rail (150; 250) togetherwith the work piece (11) by moving along a linear axis (J₁) of thelinear mechanism (110; 210.1, 210.2) and/or by moving around at leastone swivel axis of the at least three swivel axes (J₂, J₃, J₄) of thearticulated mechanism (130; 230.1 230.2); d) transferring the work piece(11) by moving the transfer rail (150; 250) along a main transferdirection (9) by moving the articulated mechanism (130; 230.1 230.2)and/or the linear mechanism (110; 210.1, 210.2); e) lowering thetransfer rail (150; 250) together with the work piece (11) by moving thelinear mechanism (110; 210.1, 210.2) and/or the articulated mechanism(130; 230.1 230.2); and f) releasing the work piece by actuating thegrippers (152; 252) of the transfer rail (150; 250).
 16. The method asrecited in claim 15, characterized in that the lifting and lowering ofthe transfer rail (150) is exclusively accomplished by moving thearticulated mechanism (130) and in that the transfer along the maintransfer direction (9) is exclusively accomplished by moving the linearmechanism (110).
 17. The method as recited in claim 15, characterized inthat the lifting and lowering of the transfer rail (250) is exclusivelyaccomplished by moving the linear mechanism (210.1, 210.2) and in thatthe transfer along the main transfer direction (9) is exclusivelyaccomplished by moving the articulated mechanism (230.1, 230.2).
 18. Useof an articulated robot having at least three parallel swivel axes (J₂,J₃, J₄) for transporting work pieces (11) in a press (1), whereby therobot is attached to a linear mechanism (110; 210.1, 210.2) fixed to apress frame (2) of the press (1) such that it is linearly movable withrespect to the press frame (2), and whereby the robot is carrying atransfer rail (150; 250) having a plurality of grippers (152; 252) forgripping the work pieces (11).